PowerFlarm v3.40

On Friday, April 18, 2014 7:16:26 AM UTC-7, Andy wrote:
On Sunday, April 13, 2014 6:18:09 PM UTC-7, Ramy wrote:

Since you don't have a transponder just set the transponder parameter to negative in the config file and nothing will get suppressed.

You will need to switch to latest firmware sooner or later since previous one will expire.


Ramy

Do you know if FLARM are working this? The suppression of same altitude mode C targets is a really poor solution to the spurious own transponder alerting problem.


Suppression of the local Mode C transponder is done by suppressing same-altitude Mode C targets. That's the main bit of info that the system has to use to do that suppression of the local transponder. Flarm can do things to try to minimize suppression of other transponders but unlike Mode S there is no hard-guaranteed way to suppress only the local Mode C transponder. So this is always going to involve a lot of art as well as science.

Mode S is a different beast where you have a unique ICAO address on each Mode S interrogation. But even a Mode S transponder has to reply to legacy Mode A/C interrogations, and if those are happening then you are back in the same boat. Given that Flarm have been tweaking stuff related to this in recent firmware releases and are warning about same altitude Mode C suppression in 3.4 then I'd assume they are still working on improving all this.

If your or other gliders in the area have Mode S transponders make sure that PowerFLARM and the Mode S transponders in all the gliders are properly configured with the correct ICAO address for those aircraft. And if there is no local transponder follow the advice Ramy already offered.

I suspect that in practice, suppressing transponders at the exact same altitude will have no much affect on PCAS reliability, as relative altitude between aircrafts fluctuate all the time, especially with gliders, and I suspect the suppression algorithm can detect altitude fluctuation and does not suppress it. This is just my guess based on the fact that my PF seem to do good job with PCAS alert even when flying at the same altitude as someone else.

Ramy

On Saturday, April 19, 2014 1:31:15 AM UTC-7, Ramy wrote:
"I suspect that in practice, suppressing transponders at the exact same altitude will have no much affect on PCAS reliability, as relative altitude between aircrafts fluctuate all the time, especially with gliders, and I suspect the suppression algorithm can detect altitude fluctuation and does not suppress it. This is just my guess based on the fact that my PF seem to do good job with PCAS alert even when flying at the same altitude as someone else."

The relative altitude between gliders may be subject to large fluctuations. The relative altitude between powered aircraft is quite likely not to vary by more that the typical 100ft resolution of the altitude encoder interface.

I have first hand experience of being on a same altitude, opposite heading, less that 500ft lateral offset threat. ZAON PCAS alerted. I acquired the aircraft visually then checked PF portable. The target was never indicated or alerted.

ZAON used, perhaps inter alia, the signal strength to determine if a mode C signal is own ship. That is why there is provision in the calibration menus for adjusting each unit for own transponder signal strength. To the best of my knowledge FLARM units have no such provision for user calibration.

Andy

It would be nice to have the option to include a list of transponder codes that were always suppressed. For example, 1202. One could make the determination if a majority of the local gliders with a transponder also had FLARM. If that was a reasonable assessment for your location, then suppressing all the 1202 hits would potentially reduce the false alarms based on transponders and would rely on the more reliable FLARM data.

On Saturday, April 19, 2014 2:49:22 PM UTC-7, wrote:
It would be nice to have the option to include a list of transponder codes that were always suppressed. For example, 1202. One could make the determination if a majority of the local gliders with a transponder also had FLARM. If that was a reasonable assessment for your location, then suppressing all the 1202 hits would potentially reduce the false alarms based on transponders and would rely on the more reliable FLARM data.

Ah the trouble there is you cannot definitively associate a Mode A squawk reply with the same transponder doing a Mode C reply. And there will be situations where targets are doing Mode C only replies (e.g. any time a target is being interrogated by TCAS I or II but out of range of ground SSR... which I'm guessing happens a fair amount).

The 'best' you could do in that situation is stop all PCAS warnings. That may be/is likely too drastic, you can also so try adjusting the PCAS height/range parameters. Ultimately there is nothing you can do that is goign to work that well with Mode C transponders. Hopefully over time this will go away as an issue as Mode S transponder use keeps growing in the USA glider fleet.

There is no need/strong justification to replace a Mode C today, they work great for letting ATC know where you are and with TCAS, TCAD and PCAS in GA aircraft etc. but on the other hand there is no sane reason to buy a new Mode C transponder today. The possible issues here with PowerFLARM interoperability is just one of those reasons. Over time and as equipment ages and gets expensive to repair and new Mode S transponder technology hopefully keeps falling in cost and size etc. we'll just see the current Mode C usage in the glider fleet migrating over to Mode S. I'm much less worried about Mode C vs. Mode S than I am to encourage *any* transponder use in areas of high airline, fast jet, and even GA traffic.

Anybody who what my opinion on what the FAA should have really done with Mode S vs. Mode C transponders and ADS-B Out carriage mandates, etc. is welcome to buy me a six pack of beer and put up with an hour of whining.

Of course you all know that I'm not a Flarm guy.

Having said that, it strikes me funny that nobody seems to have noticed that
it's the "same altitude" aircraft that's going to hit you. Why would you
want all transponders at co-altitude to be suppressed? And the notion that
you're going to be OK since the Flarm will point out other Flarm traffic.
Listen up, Guys: GA, military, and airlines are NOT using Flarm. Oh, and
we have at least one guy at Moriarty who has a Flarm but not a transponder.
So he and the half dozen or so Flarm equipped gliders can avoid each other
but he's cruising along blissfully unaware that ATC can't see him, nor can
the airliners or military flights that buzz in and out of ABQ daily.

Hopefully Flarm will work this out as Zaon did several years ago.


"darrylr" wrote in message
...
On Saturday, April 19, 2014 2:49:22 PM UTC-7, wrote:
It would be nice to have the option to include a list of transponder codes
that were always suppressed. For example, 1202. One could make the
determination if a majority of the local gliders with a transponder also
had FLARM. If that was a reasonable assessment for your location, then
suppressing all the 1202 hits would potentially reduce the false alarms
based on transponders and would rely on the more reliable FLARM data.

Ah the trouble there is you cannot definitively associate a Mode A squawk
reply with the same transponder doing a Mode C reply. And there will be
situations where targets are doing Mode C only replies (e.g. any time a
target is being interrogated by TCAS I or II but out of range of ground
SSR... which I'm guessing happens a fair amount).

The 'best' you could do in that situation is stop all PCAS warnings. That
may be/is likely too drastic, you can also so try adjusting the PCAS
height/range parameters. Ultimately there is nothing you can do that is
goign to work that well with Mode C transponders. Hopefully over time this
will go away as an issue as Mode S transponder use keeps growing in the USA
glider fleet.

There is no need/strong justification to replace a Mode C today, they work
great for letting ATC know where you are and with TCAS, TCAD and PCAS in GA
aircraft etc. but on the other hand there is no sane reason to buy a new
Mode C transponder today. The possible issues here with PowerFLARM
interoperability is just one of those reasons. Over time and as equipment
ages and gets expensive to repair and new Mode S transponder technology
hopefully keeps falling in cost and size etc. we'll just see the current
Mode C usage in the glider fleet migrating over to Mode S. I'm much less
worried about Mode C vs. Mode S than I am to encourage *any* transponder use
in areas of high airline, fast jet, and even GA traffic.

Anybody who what my opinion on what the FAA should have really done with
Mode S vs. Mode C transponders and ADS-B Out carriage mandates, etc. is
welcome to buy me a six pack of beer and put up with an hour of whining.

I am pretty sure that the suppression is based on power as well, in addition to altitude. So only a strong signal at the same altitude will be suppressed. Which mean you will still get warning for same altitude until the other aircraft is very close, giving you enough warning. I assume this is the same way that Zaon works. But again this is just my guess. Will be nice if Flarm folks will comment on this.

Ramy

Dan -

The statistics show over and over that glider-to-glider collisions are more of a threat than glider-to-GA/Miliatry. FLARM isn't intended to be a perfect solution; it's intended to provide a very reliable, medium-cost, low-power solution for the biggest collision threat: other maneuvering gliders.

Mode C and even Mode S systems are not well-suited for combating glider-on-glider carnage when the craft are in close proximity and maneuvering.

There simply is no perfect solution; but I for one will take the single solution that reasonably covers the broadest range of targets and situations - and right now that's a PowerFLARM.

--Noel

On Sunday, April 20, 2014 10:14:46 AM UTC-5, Dan Marotta wrote:

Listen up, Guys: GA, military, and airlines are NOT using Flarm. Oh, and

we have at least one guy at Moriarty who has a Flarm but not a transponder.

So he and the half dozen or so Flarm equipped gliders can avoid each other

but he's cruising along blissfully unaware that ATC can't see him, nor can

the airliners or military flights that buzz in and out of ABQ daily.

Blissfully unaware? Well, since GA, military, and airliners are pretty much all using either Mode A/C, Mode S, or ADS-B, that PFlarm-only guy is probably fully aware of the location of any potentially threatening traffic in his vicinity - even that VFR doctor in the Bonanza squawking 1200 and not talking to anybody...

And he is also aware of where all his gliding buddies are - and that's a lot of fun, too! - even the clueless new guy who it trying to run into him under his nice Cu in the middle of nowhere.

So while I agree that if you routinely mix in with high-speed airline traffic (common out West, not as common in most of midwest or east) a transponder is a smart thing, I think that a PFlarm is even more of a good thing. Both is best.

Try it - you might like it. Seriously.

Cheers,

Kirk

On Sunday, April 20, 2014 8:14:46 AM UTC-7, Dan Marotta wrote:
it strikes me funny that nobody seems to have noticed that
it's the "same altitude" aircraft that's going to hit you.


It's not that nobody has noticed. I have posted about this issue before.

The reason FALRM implemented this change is that it is less bad than having continuous alerting to ownship transponder.

Why would you want all transponders at co-altitude to be suppressed?

Because they have not figured out how to suppress the only co-altitude transponder that needs to be suppressed - the one in the same aircraft as the Power FLARM.


Andy